1. Field of the Invention
This invention relates to liquid pumps and liquid systems and more particularly to a valve and system to prevent a motor driving a liquid pump from cycling, that is quickly and repeatedly turning off and on. Owners and operators of water systems have ordinary skill in the art of this invention.
2. Description of the Related Art
Many water pumps supply water to a system having irregular, intermediate use. Often these water pumps supply water into a small reservoir such as a pressure tank. Water systems normally have a range of operating pressures. For example, the range of water of pressures is set between 40 and 60 p.s.i.. This pressure range is normally achieved with a pressure switch which cuts off the motor to the pump at 60 p.s.i. and then turns it on at a pressure of 40 p.s.i. If the use is such that the small pressure tank is quickly drained, the motor is switched on, the pump fills the pressure tank quickly, the pump switches off, and then as the tank is quickly drained, the pump switches on again. Most of the wear and damage to the motors and the pumps is caused by the numerous repeated starts and stops of the system.
Such a system as described is common on residential water supplies having a separate water supply for every residence, as often occurs in rural areas. Also the problem arises in systems that have irregular irrigation, for example, golf courses where different flow rates are required. Some systems with cycling problems have multiple pump stations which are activated according to the different supplies of water needed. Also the system with cycling problems exists with tall buildings where because of the building height it is necessary to have controls for different levels of the building, and different flow rates.
The problem also exists in liquid systems other than water. For example, the ordinary gasoline fuel dispenser at an auto service station has an electric motor driven pump which delivers fuel to a small pressure tank, then to a metering device, and then to the manually controlled nozzle. When the auto tank is nearly full the customer will often reduce the flow to a dribble to "top off" the tank. This will cause the motor to cycle on and off.
Constant outlet pressure valves are well known to the art. Such valves are designed to reduce the flow if the outlet pressure is above the optimum range and to completely stop the flow when it exceeds the preset pressure.
Before this invention, attempted solutions to alleviate this problem included installing a constant outlet pressure valve with a small bypass around the constant outlet pressure valve. The valve is installed downstream of the pump and upstream of the reservoir and pressure switch. For example, if the normal flow is fifteen gallons per minute, the bypass provides a flow of one gallon per minute. Therefore, when there is a small volume of flow, the liquid will continue to trickle through the bypass and slowly refill the reservoir. When the reservoir is sufficiently full, the pressure switch will shut the motor off. The reservoir will supply the need until the water flow again reaches levels so that the pressure switch closes, starting the pump motor to fill the reservoir. However, these bypasses exhibited certain problems, one of which being the noise caused by the pressure of the liquid flowing through a small opening. Also, the small opening is susceptible to debris cloggage.
My previous grandparent and parent applications, referenced above, solved this problem by cutting a notch in one of the seating surfaces on either the valve seat or the valve device. Therefore, when the valve is closed, the trickle flow is through this notch. Experience has shown that this will not be a noisy flow, nor will it clog. Each time the valve opens debris which might collect in the restricted flow device (the notch) is flushed out by the opening of the valve and the flow of liquid across the notched surface.
With some installations this may cause another problem. When the down stream (reservoir) pressure reaches the pressure switch turn off level the down stream pressure exceeds the upstream pressure; this causes a back flow through the notch and through the pump. In most installations the back flow through the pump causes the pump to spin backwards. When the motor is energized with the pump spinning backward the shaft between the pump and motor may break.
An obvious solution includes placing a check valve between the pump and reservoir. This solution requires additional elements to be added to the systems.